As shown in FIG. 1, the micro motor includes a hub 10, a rib structure 20, an inner ring 30, an outer ring and at least two micro actuators 50.
Furthermore, together with the reference to FIG. 2, low-stress (250 MPa) Si3N4 is deposited on a substrate 60 by LPCVD (Low Pressure Chemical Vapor Deposition) to serve as an insulation layer 61.
The hub therein is a stationary member fixed on the insulation layer 61 and takes the form of hollow ␣-like disk, and its top edge is projected outwardly to form a top lid 11.
The rib structure 20 and the inner ring 30 are all in form of hollow ring. The inner ring 30 is located around the top lid 11, and the hole diameter of the inner ring 30 shall be slightly greater than the maximal outer diameter of the top lid 11. The rib structure 20 is fixed to the bottom portion of the inner ring 30 and is located beneath the top lid 1, its bottom surface has a plurality of bumps 21 for supporting the inner ring 30 to rotate above the insulation layer 51, and the diameter of the inner hole of the rib structure 20 shall be greater than the outer diameter of the hub 10 but smaller than the hole diameter of the inner ring 30 and the maximal outer diameter of the top lid 11, so that the top lid 11 is located above the rib structure 20 to serve as a stopper for preventing the rib structure 20 from coming off as a result of rotation.
The outer ring 40 is also in form of hollow ring, and the hole diameter of the outer ring 40 shall be far greater than the maximal outer diameter of the inner ring 30. A plurality of micro actuators 50 are located between the inner ring 30, the outer ring 40 and are connected with the inner ring 30 and the outer ring 40 by a respective cantilever beam 51, and a bushing 52 and an actuator plate 53 are disposed on each cantilever beam 51.
An upper and a lower electrodes 62, 63 are disposed on the insulation layer 61. When a fixed driving voltage is given, the actuator plate 53 is deflected due to the attraction of electrostatic force. After the given voltage is removed, the energy of the tensile stress stored in the actuator plate 53 pushes the micro actuator 50 to displace in completion of a step motion (the actuation concept of micro actuator is a prior art and is briefly depicted herein).
When the micro actuator 50 drives the rib structure 20, the inner ring 30 and the outer ring 40 to rotate, conventional micro motor will generate in non-directional wobble and deviation during rotation for sake of the gap existing between the hub 10 and the rib structure 20, which causes serious surface contact and abrasion among the rib structure 20, the hub 10 and the top lid 11. Especially when the size of micro actuator motor is usually less than 2×2 (mm), the surface contact and abrasion among the rib structure 20, hub 10 and top lid are prone to abrasion and failure of parts more easily.